Homestead on Windows 8.1, Can't execute composer update

I followed all the steps of the documentation, but to execute the command below appears this message

$ homestead up
Bringing machine 'default' up with 'virtualbox' provider...
==> default: Importing base box 'laravel/homestead'...
No base MAC address was specified. This is required for the NAT networking
to work properly (and hence port forwarding, SSH, etc.). Specifying this
MAC address is typically up to the box and box maintainer. Please contact
the relevant person to solve this issue.

If I run again, the VM is started and show this ( success )

$ homestead up
Bringing machine 'default' up with 'virtualbox' provider...
==> default: Checking if box 'laravel/homestead' is up to date...
==> default: Setting the name of the VM: homestead
==> default: Clearing any previously set network interfaces...
==> default: Preparing network interfaces based on configuration...
    default: Adapter 1: nat
    default: Adapter 2: hostonly
==> default: Forwarding ports...
    default: 80 => 8000 (adapter 1)
    default: 443 => 44300 (adapter 1)
    default: 3306 => 33060 (adapter 1)
    default: 5432 => 54320 (adapter 1)
    default: 22 => 2222 (adapter 1)
==> default: Running 'pre-boot' VM customizations...
==> default: Booting VM...
==> default: Waiting for machine to boot. This may take a few minutes...
    default: SSH address: 127.0.0.1:2222
    default: SSH username: vagrant
    default: SSH auth method: private key
    default: Warning: Connection timeout. Retrying...
    default: Warning: Remote connection disconnect. Retrying...
    default:
    default: Vagrant insecure key detected. Vagrant will automatically replace
    default: this with a newly generated keypair for better security.
    default:
    default: Inserting generated public key within guest...
    default: Removing insecure key from the guest if it's present...
    default: Key inserted! Disconnecting and reconnecting using new SSH key...
==> default: Machine booted and ready!
==> default: Checking for guest additions in VM...
    default: The guest additions on this VM do not match the installed version of
    default: VirtualBox! In most cases this is fine, but in rare cases it can
    default: prevent things such as shared folders from working properly. If you see
    default: shared folder errors, please make sure the guest additions within the
    default: virtual machine match the version of VirtualBox you have installed on
    default: your host and reload your VM.
    default:
    default: Guest Additions Version: 5.0.4
    default: VirtualBox Version: 4.3
==> default: Setting hostname...
==> default: Configuring and enabling network interfaces...
==> default: Mounting shared folders...
    default: /vagrant => C:/Users/xxx/AppData/Roaming/Composer/vendor/laravel/homestead
    default: /home/vagrant/Code => C:/Users/xxx/Code
==> default: Running provisioner: file...
==> default: Running provisioner: shell...
    default: Running: inline script
==> default: ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC7WxXs8aoCAev3sVfP5FV7jXfDWCFg3BC3ggfeAWfy7bv8Ebjn3akqzQ1ZY5Uko0P                                                              CY/rAKK+zdb9NscOGI1kRnEfu4SDzNIDrPeLXS2r8vKeJqH22qGtjO40IroFAlAve7XUahohUdVUxbHwT+1YJmfKdd7WTKxcoHLGi1aevTy1lFcCOilD                                                              uUYXde39Ohw+IC62jM5BIC9dSc7fg5Mj4ntTYXaMKLsBBLJ2Y68ePaZlLty4y/z7OFRb0qKjmEEBKtjVJk1t18kB6IdpeUt/kiiBT7acglJEPPkUNCel                                                              /kjAYPsJhb72P8piRIlmFGZKj34Zu+vl8TjISH/8MCltX user@homestead
==> default: Running provisioner: shell...
    default: Running: inline script
==> default: Running provisioner: shell...
    default: Running: C:/Users/xxx/AppData/Local/Temp/vagrant-shell20151014-5916-6daa0i.sh
==> default: Running provisioner: shell...
    default: Running: C:/Users/xxx/AppData/Local/Temp/vagrant-shell20151014-5916-e1xqlv.sh
==> default: nginx stop/waiting
==> default: nginx start/running, process 1817
==> default: php5-fpm stop/waiting
==> default: php5-fpm start/running, process 1832
==> default: Running provisioner: shell...
    default: Running: C:/Users/xxx/AppData/Local/Temp/vagrant-shell20151014-5916-e9cvop.sh
==> default: Warning: Using a password on the command line interface can be insecure.
==> default: Running provisioner: shell...
    default: Running: C:/Users/xxx/AppData/Local/Temp/vagrant-shell20151014-5916-1sr069i.sh
==> default: createdb: database creation failed: ERROR:  database "homestead" already exists
==> default: Running provisioner: shell...
    default: Running: C:/Users/xxx/AppData/Local/Temp/vagrant-shell20151014-5916-alwrsf.sh
==> default: Running provisioner: shell...
    default: Running: inline script
==> default: Running provisioner: shell...
    default: Running: inline script
==> default: Running provisioner: shell...
    default: Running: inline script
==> default: php5-fpm stop/waiting
==> default: php5-fpm start/running, process 1922
==> default: Running provisioner: shell...
    default: Running: inline script
==> default:                                                                                                                                                                      
==> default:   [Composer\Downloader\TransportException]                                                                                                                           
==> default:   The "https://getcomposer.org/version" file could not be downloaded: php_network_getaddresses: getaddr                                                              info failed: Name or service not known
==> default:   failed to open stream: php_network_getaddresses: getaddrinfo failed: Name or service not known                                                                     
==> default:                                                                                                                                                                      
==> default: self-update [-r|--rollback] [--clean-backups] [--no-progress] [version]
The SSH command responded with a non-zero exit status. Vagrant
assumes that this means the command failed. The output for this command
should be in the log above. Please read the output to determine what
went wrong.

I'm using Windows 8.1, I am in the work and there is a proxy but I think this is not the problem